Wireless communication networks are a ubiquitous part of modern life in many areas. A number of different wireless communication protocols for communication on radio links have been developed. For example, the Third Generation Partnership (3GPP) Long Term Evolution (LTE) is a set of enhancements to the 3GPP Universal Mobile Telecommunications System (UMTS) that supports high data rates, low latency, low implementation and operating costs, and a seamless connection to legacy wireless communication networks. As another example, the 3GPP Wideband Code Division Multiple Access (WCDMA) is a wideband spread-spectrum channel access protocol utilizing direct-sequence spread spectrum technology and unique codes to multiplex multiple users over a single wide frequency channel. 3GPP High Speed Packet Access (HSPA) is an extension of WCDMA protocols. HSPA transmits communication data on shared channels, in packets addressed to specific users. HSPA features short Transmission Time Interval (TTI), link adaptation, fast scheduling, fast retransmission and soft-combining, and advanced modulation, resulting in increased data rates, low latency, and increased system capacity. Yet another example of a widely-deployed protocol is the 3GPP Global System for Mobile communications (GSM). 3GPP General Packet Radio Services (GPRS) is a packet data service extension to GSM. 3GPP Enhanced Data rates for GSM Evolution (EDGE) is a 3G extension to GSM that increases the capacity and performance of GSM and GPRS networks.
Accurately determining the location of a mobile user within a communications network is an ongoing challenge. Government mandates, such as the United States Federal Communications Commission (FCC) Enhanced 911 (E-911) positioning requirements in North America, and commercial Location Based Services (LBS) demand rapid and accurate determination of the location. The E-911 requirements nowadays call for horizontal accuracy better than 50 m and vertical accuracy better than 3 m indoors. Several positioning techniques of varying accuracy and complexity are known in the art. These include Cell Identification (ID) positioning, Round Trip Timing (RTT) positioning, Time Of Arrival (TOA) positioning, Angle Of Arrival (AOA) positioning, Time Difference of Arrival (TDOA) positioning, Assisted Global Positioning System (A-GPS) positioning.
A particular technique is fingerprinting positioning, see WO 2011/040856 A1. Fingerprint positioning typically relies on a snapshot of various properties of the radio link which is specific for the location. The various properties can, in some scenarios, include RTT, TDOA, A-GPS, and cell-ID data. Fingerprint positioning techniques are thus based on comparing a plurality of location-specific downlink properties of the radio link and/or a plurality of location-specific uplink properties against a database of location-specific fingerprints (fingerprint database), each fingerprint being associated with a respective location within the wireless communication network. The fingerprint database is typically populated based on reference measurements of the plurality of location-specific uplink and/or downlink properties of the radio link and reference measurements of the associated location. Fingerprint positioning techniques allow determining the location at a comparably high precision.
However, known fingerprint positioning techniques face certain restrictions and drawbacks. E.g., in a typical indoor environment, the properties of the radio link may strongly vary as a function of location; this may be due to one or multiple reflections at walls of the indoor environment. A typical example are glass fronts being present in, e.g., malls, offices, shops, and manufacturing plants. One the one hand side, such a strong location-dependency of the properties of the radio link offers the potential of highly accurate positioning based on fingerprinting techniques. On the other hand side, in such an environment, reference implementations of the fingerprinting positioning technique sometimes achieve poor accuracy where the fingerprint database is populated with inaccurate reference measurements.